White LEDs are expected to be applied to illumination uses as light sources of the next generation which are to be used in place of incandescent lamps or fluorescent lamps.
In LED devices using a fluorescent substance to carry out conversion of wavelengths, a fluorescent substance powder is blended in, for example, a mold resin made of an organic type binder resin that seals a luminous plane of an LED chip to mold and a part or all of the emission from the LED chip is absorbed to carry out conversion into a desired wavelength.
However, there is a problem that the mold resin constituting the above LED device is deteriorated by high power short-wavelength light which is in the blue to ultraviolet region, causing discoloration.
In order to solve the above problem, Patent Reference 1 discloses a method for coating an LED chip by dispersing a fluorescent substance in a non-lead type low-melting point glass such as an SnO2—P2O5 type glass or a TeO type glass.
Also, Patent Reference 2 discloses use of a fluorescent substance composite glass obtained by molding a glass powder and an inorganic fluorescent substance powder under pressure and baking the molded material to make glass, and dispersing a fluorescent substance powder in the glass.
Patent Reference 1: Publication of JP-A 2005-11933
Patent Reference 2: Publication of JP-A 2003-258308